Astable multi vibrator using transistor

Dear All
I have used the given circuit, Its quiet working well. When i change the the polarity of the capacitor it does not work.I have gone through the literature, but there is no proper explanation on the polarity.
Please answer it.

ThanksView attachment multi.BMP

Most electrolytic capacitors are polarized and require one of the electrodes to be positive
relative to the other; they may catastrophically fail if voltage is reversed.
This is because a reverse-bias voltage above 1 to 1.5 V will destroy the center layer of
dielectric material via electrochemical reduction (see redox reactions).
Following the loss of the dielectric material, the capacitor will short circuit,
and with sufficient short circuit current, the electrolyte will rapidly heat up and either
leak or cause the capacitor to burst, often in a spectacularly dramatic fashion.

More............
Electrolytic capacitor - Wikipedia, the free encyclopedia

After this redox reaction capacitor act more resistive ie. capacitor parallel resistance
increases and capacitance value decreases.

In this FF-circuit Rb=100k . When capacitance parallel resistance is eg. 10kohms,
transistors bias points are not correct and circuit can not oscillate.


KAK

hey guys!
Hi
In astable multivibrator , capacitors used as positive feedback. if you reverse their polarity, they will destroy(their dielectric)
the feed back road is from collector of q1 to the base of q2 . thus collector is more positive than base . because of that , the potential of base is: base emitter voltage( because emitter is grounded) thus voltage of base approximately is 0.7 volt. so collector voltage is higher than base voltage . and electrolytic capacitors cant work as well as in reverse bias.
Best lucks
Goldhen

Thanks a lot to KAK.
Will you please write me that in What way the capacitor polarity does not work in circuit when the polarity is reversed?

This guide is a full handbook on aluminum electrolytic capacitors.
I recommend that you read this booklet completely.

Characterization CIRCUIT MODEL page 5.
Polarity – Reverse Voltage page 13.

**broken link removed**


You noticed, that the electrolytic capacitor model has a zener connected in parallel with the capacitance value.
Another thing is the chemical reactions caused by inverse voltage in the electrolyte

Both caps (10ufd) have the neg. terminals returned to base terminal which can never rise above 0.6VDC .The pos . terminal goes to Vcc when the transistor switches OFF in the astable ckt .
As such , the ckt works with the elcos properly biased .We can use a bipolar electrolytic cap if you want to see reverse caps usage .
Alternately , we can use a polyester cap which is bipolar ..

A real good astable inverter can be fabricated by hex inverter 7606 using two units and two resistors .